A major problem constantly faced by engineers in the polymer reaction engineering field is to accurately predict the performance of continuous polymerization reactors. Due to the critical commercial application of polymers, the polymerization reaction should be very carefully controlled in order to insure uniform properties. However, most commercial installations lack proper on-line techniques to predict the product behavior as it is made in the reactor. A number of parameters such as hold-up time, pressure and temperature profile in the reactor are key factors affecting reactor and product performance. Also, product properties are affected by reactor start-up, shut-down and rate changes. There is indeed the need for a quick, continuous on-line measurement of polymer properties. As an on-line analyzer of polymer properties has not been demonstrated, the approach of using computational fluid dynamics techniques, elementary measurement of temperature, pressure and flow by means of in-line instruments and computer hardware (DCS, VAX 8000) have proven successful. Off-line verification of model predictions by means of a Liquid Chromatograph is then easily done.
This invention provides on-line real time polymer product properties as the polymer is being made in the reactor without making use of the chemistry of the reacting system. In fact, to follow the kinetics of the reaction for making polymer properties prediction has proven to be an approach without recognizable value, mostly for the reason that energies of activation and reaction rate constants for the reaction system are hard to measure accurately and, therefore, the numerical solution of the set of differential equations is inaccurate. Also, the polymerization chemistry might not be well understood, in particular, the kinetics of cyclic dimer and oligomer formation.
The present invention deals with the application of fundamental principles of fluid mechanics and polymer processing that were used in the on-line prediction of molecular weight average (Mw), molecular weight number average (Mn) and polydispersity (Mw/Mn) in a continuous tubular polymerization reactor.